The present invention relates to network congestion, and more specifically, to adaptively determining the equilibrium set point for a quantized congestion notification (QCN) protocol to prevent instability or a race condition between a priority flow control (PFC) protocol and a QCN protocol on converged Ethernet links. The present invention may also apply to virtualized CEE-like Software Defined Networks (SDN).
IEEE 802.1 data center bridging (DCB) Ethernet is often used as a primary physical network protocol in datacenters for computer-to-computer communications. In contrast to the modern 802.1Qau DCB (i.e., convergence enhanced Ethernet (CEE)/data center Ethernet (DCE)), the traditional Ethernet was typically designed to be a best-effort network and may experience network congestion. Network congestion occurs when a link or node is carrying so much data that its quality of service deteriorates. Typical effects include queueing delay, packet loss and/or the blocking of new connections. A consequence of packet loss or the blocking of new connections is that incremental increases in offered load only lead to small increases in network throughput or to an actual reduction in network throughput. Moreover, network congestion may lead to a congestive collapse at a choke point in the network, where the total incoming traffic to a node exceeds the outgoing bandwidth. When a network is in such a condition, there are high levels of packet delay and loss and general quality of network service is poor. These effects are aggravated in the modern multitenant datacenters using server and network virtualization on top of Layer 2 CEE fabrics with Priority Flow Control (PFC, 802.1Qbb), used for converged lossless traffic. Hence the need for Quantized Congestion Notification (QCN, 802.1 Qau), which is today built in most modern CEE switches and adapters, as well as being introduced in the new Virtual Overlays and software-defined networking (SDN) solutions.